Equity-Based Compensation, Profit Sharing and Deferred Compensation Plans - Equity-Based Compensation Plans (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Stock Options
Stock Option, Shares
Outstanding at beginning of period (Shares)	1,076,000
Granted (Shares)	30,000
Exercised (Shares)	(159,000)
Forfeited (Shares)	(31,000)
Outstanding at end of period (Shares)	916,000
Exercisable at end of period (Shares)	461,000
Weighted Average Per Share Exercise Price
Outstanding at beginning of period (Weighted Average Exercise Price) | $ / shares	$ 1,048.38
Granted (Weighted Average Exercise Price) | $ / shares	2,431.54
Exercised (Weighted Average Exercise Price) | $ / shares	886.41
Forfeited (Weighted Average Exercise Price) | $ / shares	1,099.68
Outstanding at end of period (Weighted Average Exercise Price) | $ / shares	1,119.92
Exercisable at end of period (Weighted Average Exercise Price) | $ / shares	$ 957.50
Remaining Contractual Life and Aggregate Intrinsic Value
Outstanding at end of period (Weighted Average Remaining Contract Life (Years)	6 years
Exercisable at end of period (Weighted Average Remaining Contract Life (Years)	5 years
Outstanding at end of period (Aggregate Intrinsic Value) | $	$ 2,187,430
Exercisable at end of period (Aggregate Intrinsic Value) | $	$ 1,176,843
2010 Equity Incentive Plan | Stock Options
Stock Option, Shares
Outstanding at end of period (Shares)	208,000
2010 Equity Incentive Plan | RSUs
RSU, Shares
Outstanding at beginning of period (Shares)	16,000
Granted (Shares)	0
Vested (Shares)	(6,000)
Forfeited (Shares)	0
Outstanding at end of period (Shares)	10,000
Vested, but not issued at end of period (Shares)	5,000
Remaining Contractual Life and Aggregate Intrinsic Value
Outstanding at end of period (Aggregate Intrinsic Value) | $	$ 34,945
Vested, but not issued at end of period (Aggregate Intrinsic Value) | $	$ 18,344